Generally, parts washers used to clean parts, such as automotive parts, utilize a cabinet having a fluid holding space and a parts washing chamber above the fluid holding space. Normally, the fluid holding space is separated from the parts washing chamber by a false floor having a perforate section therein to allow fluid sprayed against the parts to return to the fluid holding space. A heat source is provided in the fluid holding space to heat the fluid before the pump system is started to deliver pressurized heated fluid to a fluid spray structure for delivering the heated pressurized fluid to against the parts to be washed.
Normally, an access reservoir is provided exteriorly of the parts washing chamber such that the fluid holding space has an internal fluid holding space portion and an external fluid holding space portion in the form of the access reservoir. The access reservoir has a removable cover thereon so that cleaning chemicals can be added to the fluid and so that various other service functions can be performed on the parts washer mechanisms in the access reservoir.
Upon heating the fluid in the fluid holding space at startup, there is a temperature differential between the heated fluid and the air thereabove. The false floor helps to insulate the heated fluid from the air, thereby contributing to the temperature differential in the cabinet.
Due to this temperature differential, when the pump system is started and the first charge of heated, pressurized cleaning fluid is discharged from the fluid spray structure, the air in the cabinet will experience a rapid increase in temperature thereby expanding the air in the cabinet. This sudden expansion of air can cause a water-hammer effect such that potentially damaging pressure waves in the cleaning fluid may be formed. The sudden air expansion can also cause a wave of heated cleaning fluid to be forced out of the cabinet and into the access reservoir with such force as to cause the removable cover to dislodge thereby allowing significant quantities of heated fluid to spill out onto the floor surrounding the parts washer.